Seeking Advice on Waterproofing Custom Built Wood Trays

[LFLarry]

I am in the process of making some all wood trays for normal darkroom processing (dev, stop, fix, wash) and want to know the best way to water/chemical proof the trays?

Thanks in advance.

Larry

[willwilson]

I have a set of 30x40 wood trays I built. They see limited use. They are painted with several coats of water based polyurethane. Works well and poly is easy to work with.

If they were more frequently used I would have epoxied them. I use west systems but there are other options too. If super heavy duty, you could add some fiberglass cloth. West systems has lots of info on their website.

[Eric Woodbury]

I've used the West. It's very good. I've heard good things about having them sprayed with truck bed liner stuff. Many years ago when I had no money, my friend and I made a cardboard sink and covered it in fiberglass resin. Lasted 7 years and then I moved.

[MrFujicaman]

Ditto on the truck bed liner. I built my darkroom sink with it 5 years ago and it's never leaked.

[Willie]

Rubber shower pan liner pushed in place and folded over the sides works - also for a full sink.

Sheets of plastic work. Lay it in, fill the tray and empty later and throw it out as it wears.

[lab black]

West and fiberglass. 25 years and my sink hasn't had a single leak.

[Jim Noel]

I built my plywood sink in 1989 using 3 coats of West Systems 2 part epoxy. It still serves me well. No fiberglass.

[John Layton]

Built my sink and large trays with Rakka epoxy (less expensive than West) over birch ply…super smooth, tough as nails, and has been holding up great - with absolutely no signs of liquid infiltration.

[HMG]

OK, I'll bite. Why make the trays out of wood? Odd size?

[Drew Wiley]

It's likely to be more expensive in wood. Have you checked the price of penetrating marine epoxy these days?- which is what you need. And it's nasty to work with. How about marine ply? - an already expensive product up about 400% due to pandemic shortages, unless you already have your own stash. Much simpler just to solvent-weld some ABS sheeting. West is a B-line across town from me. They bought out their competitor Smith Epoxy along the freeway, but still keep that brand going in parallel. We sold more of their epoxy products where I worked than the factory outlet itself. Gosh knows how many wooden darkroom sinks I've told people how to make. But I wouldn't do it myself, and I was in charge of the biggest Festool dealership in the country west of New England - so you can't say I don't know how to make a straight plywood cut! ...and the danged sheer weight of wooden trays. I've made oversize 30X40 acrylic trays, and those are heavy enough. But if that is what you like doing, so be it. Just do it outdoors. Both liquid epoxies and fiberglass resin give off very unhealthy vapors. Avoid skin contact as well.

[Greg Y]

I haven't built trays, but i've had two darkrooms with sinks i built out of plywood & had lined with "Duradek".... (waterproof vinyl deck covering). A couple of days of good ventilation & the smell from the contact adhesive was gone

[xkaes]

Any boating/marine/sailing shop will have a variety of waterproof paints. The epoxy paints are not just waterproof, they are chemical resistant.

[Drew Wiley]

Greg - vinyl deck coatings are pretty short-lived in terms of expansion-contraction survivability, are apt to have some texture, making them hard to clean, stain like heck, and can't tolerate any kind of hot solvent like acetone. Can't recommend them. But someone with industrial roofing skills could heat-weld a true hypalon rubber liner inside a sink. Liquid hypalon is so nasty to breathe that it got banned in the US long ago; I used to sell that for lining industrial plating vats. Penetrating marine or structural epoxies are really the best simple solution on plywood, as long as one is careful health-wise during the application and drying phase. But unlike paints, they cure rather quickly.

If I were still young and ambitious, it might be fun to create a custom laminate waterproof ply using a big vacuum press. I sold a number of really nice German vac presses to cabinet shops just before I retired (no relation to photo drymount presses); not a toy I personally need - too expensive. But all kinds of possibilities with those, even in-house stainless laminates that can be sized down on a panel saw with the right blade, which would of course would itself cost more than a whole set of big prefab plastic darkroom trays - but what the heck. If one has the itch to make things themselves, why not?

[domaz]

I've used the West. It's very good. I've heard good things about having them sprayed with truck bed liner stuff. Many years ago when I had no money, my friend and I made a cardboard sink and covered it in fiberglass resin. Lasted 7 years and then I moved.

Making a sink out of cardboard sounds like an amazing way to save time and money building a darkroom sink. Especially if you don't need it to be permanent. I know the "proper" solution to these things is expensive Marine Epoxy but who wants to deal with the price and smell of that stuff.

[willwilson]

Mine are not really that heavy. Definitely big and bulky though. 1x4 pine frame and 1/4 plwood bottoms. All butt joints with screws, wood glue, paintable caulk, and several coats of poly. They are at least 10 years old and still going strong.

Not my prettiest work, lol.229600229601229602

[Tom Monego]

I built a sink in the in my former house, I used 1x8 pine and exterior plywood covered it with marine epoxy, 3 coats if I remember, I had it fully plumbed. It was still good when I moved out of that house 20 years later. I had to saw it in half to get it out of the room.

[xkaes]

I had to saw it in half to get it out of the room.

I made the same mistake -- making the sink INSIDE the darkroom. Of course, at the time, I never entertained the thought that I might move some day.

I still miss the three feet I had to chop off!!!